Iran Is Developing Plans for Faster, Cruder Weapon, U.S. Concludes

New intelligence about Iran’s nuclear program has convinced American officials that a secret team of the country’s scientists is exploring a faster, if cruder, approach to developing an atomic weapon if Tehran’s leadership decides to race for a bomb, according to current and former American officials.

The development comes even amid signals that Iran’s new president is actively seeking a negotiation with the Trump administration.

The intelligence was collected in the last months of the Biden administration, then relayed to President Trump’s national security team during the transition of power, according to the officials, who asked for anonymity to discuss sensitive details. The intelligence assessment warned that Iranian weapons engineers and scientists were essentially looking for a shortcut that would enable them to turn their growing stockpile of nuclear fuel into a workable weapon in a matter of months, rather than a year or more — but only if Tehran made a decision to change its current approach.

U.S. officials said they continued to believe that Iran and its supreme leader, Ayatollah Ali Khamenei, had not made that decision to develop a weapon, officials said in interviews over the past month. But new intelligence suggests that as Iran’s proxy forces have been eviscerated and its missiles have failed to pierce American and Israeli defenses, the military is seriously exploring new options to deter a U.S. or Israeli attack.

Iran, officials said, remains at the nuclear threshold. In the years since Mr. Trump pulled out of the 2015 nuclear accord, the country has resumed uranium production and now has plenty of fuel to make four or more bombs. But that is not enough to actually produce a weapon, and the new evidence focuses on the last steps Iran would need to turn the fuel into one.

The evidence is almost certainly bound to be part of the discussion on Tuesday between Mr. Trump and Israel’s prime minister, Benjamin Netanyahu. Mr. Netanyahu is the first world leader to visit the White House since Mr. Trump’s inauguration two weeks ago. For years, the Israeli leader has walked to the edge of ordering an Israeli military strike on Iran’s nuclear facilities, only to back away, often under pressure from his own military and intelligence chiefs, and the United States.

But the dynamic now is different, and Mr. Netanyahu’s calculations may be, too.

Iran has never been weaker than it is today, in the view of American and Israeli officials. Hamas and Hezbollah, which it has funded and armed, have lost their leadership and their ability to strike Israel. Syria’s leader, Bashar al-Assad, has fled to Moscow and his country is no longer an easy route for Iranian weapons.

In October, an Israeli counterstrike on Iran took out the missile defenses around Tehran and some of the nuclear facilities. It also struck the giant mixing devices that make fuel for new missiles, crippling Iranian production.

Mr. Trump has indicated that he is in no hurry to get into a direct conflict with Iran, and seems open to a negotiation. When asked just after the inauguration whether he would support an Israeli strike on the facilities, he said: “Hopefully that can be worked out without having to worry about it. It would really be nice if that could be worked out without having to go that further step.” Iran, he added, will hopefully “make a deal.”

Iran’s president, Masoud Pezeshkian, who entered office in July after his predecessor was killed in a helicopter crash, has repeatedly said that he, too, would like to negotiate a new arrangement. But history suggests he may be unaware of what the Islamic Revolutionary Guards Corps is working on as they prepare the nuclear option, former U.S. officials and Iran experts say.

“President Pezeshkian and the Iranian foreign ministry likely have no knowledge about the regime’s internal nuclear deliberations,” said Karim Sadjadpour, an expert on Iran at the Carnegie Endowment for International Peace.

“The Islamic Republic has long had two parallel regimes,” he said. “There’s a deep state of military and intelligence forces, reported to Khamenei, who oversee the nuclear program and regional proxies and are tasked with repression, hostage taking and assassinations.”

Then, he said, there are diplomats and politicians “who are authorized to speak to Western media and officials who have little if any knowledge of these activities” but are given the task of denying them.

U.S. officials have long said Iran abandoned its weapons program in 2003, after the American invasion of Iraq. Iranian government officials have similarly insisted the country is pursuing civilian nuclear technology.

Still, there is little doubt about Iran’s long-running planning to produce a weapon. Documents Israel stole in a raid on a warehouse in Tehran in 2018 described the technical efforts in detail.

If Tehran decides to change its policy and pursue a nuclear weapon, Western officials have long assessed that it would take only days for Iran to enrich uranium to a level of 90 percent, the purity typically needed to produce a bomb. It has already made enough fuel, enriched at 60 percent, to make four or five weapons.

But enriching the uranium to bomb grade is not enough for Iran to produce a nuclear weapon. And for years American officials have said it would take a year to 18 months to turn that highly enriched uranium into a sophisticated warhead capable of being mounted on a ballistic missile. Some Israeli estimates were even longer, upward of two years.

The Iranians have known for years that this long development time is a huge vulnerability. If the International Atomic Energy Agency, which still conducts limited inspections of nuclear fuel production, announced that Iran was producing bomb-grade fuel — enriched to 90 percent purity — Israel and the United States have warned in the past that they would most likely be forced to take military action.

So Iran’s best deterrent would be to convert that fuel into a working weapon. But it would not have much time.

U.S. officials believe Iran has the know-how to make an older-style nuclear weapon, one that could be put together far faster than the more sophisticated designs Tehran has considered in the past. (It most likely obtained the blueprints for such a weapon from A.Q. Khan, the Pakistani nuclear scientist who sold the country designs for its nuclear centrifuges more than a quarter century ago.)

Such a weapon would not be able to be miniaturized to fit on a ballistic missile. It would also probably be far less reliable than any more modern weapon design.

As a result, the weapon would be unlikely to be an immediate offensive threat. But such a crude weapon is the kind of device Iran could build quickly, test and declare to the world that it had become a nuclear power, U.S. officials said.

While it would be difficult to use such a weapon against Israel, it could have a deterrent effect, making countries considering an attack against Iran think twice.